Some important tips about K&N Filterchargers

Service Interval

A K&N Filtercharger is a high-performance air filter, both in terms of air flow and filtration. However, the service interval can vary widely depending on the severity of the driving conditions. The service interval can be from 100 miles, such as a desert-racing motorcycle, to 100,000 miles exemplified by a commercial semi truck. The proper way to determine when an air filter needs service is with an air restriction gauge. Such a device is commonly used on heavy duty trucks and construction equipment. A restriction gauge, or vacuum gauge, measures the pressure differential inside and outside the filter and relays the information in the form of a numeric value or a red/green, pass/fail indicator. As the filter collects more and more dirt, the restriction value increases. At a predetermined point or rate of restriction, the filter is serviced. The maximum allowable of restriction for a K&N Filtercharger is 15-inches of vacuum (water). If the restriction is allowed to go higher, the filter media might become so restricted that the element could distort allowing dirty air to bypass the filter and enter the engine. Conversely, cleaning a filter too often shorten its serviceable life expectancy.

 Service Life

A K&N Filtercharger can be washed up to 25 times before it is considered no longer serviceable. Even though the filter may not show outward signs of deterioration, it should be replaced after 25 washings. Excessive washings will deplete the tiny cotton hairs that crisscross the openings. The resulting damage will allow tiny dust particles to pass through.

Limited Warranty

K&N's warranty covers defects in materials and workmanship. Any K&N product deemed defective will be replaced free of charge. However, K&N is not responsible for damage or abuse. Nor can we be held responsible for inconsequential damage resulting from a damaged filter or a defective or damaged filtration system.


When servicing a K&N filter, take care not to over-oil the element. Besides impeding air flow, excess oil can migrate into the intake system where it can coat electronic sensors, which may hinder their operation. Never saturate the filter. If oil drips from the filter, wash it and start over. Use only K&N oil. For example, an E-1500 filter has 92.4-inches of surface area requiring 1.707 fluid ounces of oil. Follow oiling instructions included with your filter or refer to the instructions listed in the back of this catalog.

Fit and Finish

When installing a K&N filter, check all gaskets, clamps and seams for damage and/or deterioration. Check the filter's sealing surface. Do not install a filter if the seal shows signs of damage or deterioration. Check for cracks in the air box, particularly at the seams and around the corners. Such defects could cause air leakage around the filter. Also, check to insure the filter is sealing properly in the air box. A plastic air box can warp from age or continuous heat cycling. Apply a thin layer of filter grease on both sides of the seal each time the filter is installed. An impression in the grease will indicate a positive seal. Check any lines or hoses connected to the air box or adjoining hoses leading to the engine. Installed Filter Engine oil in the air box, resulting from excessive blow-by, will cause the filter to shrink and possibly lose its seal. Clean any dust or debris out of the air box with a damp cloth, making sure nothing enters the air inlet while the filter is out. Never start the engine without the filter in place. Use only K&N Air Filter Cleaner to clean your filter. Harsh household cleaners can damage the cotton material and/or the rubber seal. Check the outside of the medium for broken wires, rips or tears. Do not use an element that shows signs of damage or wear. Use K&N Air Filter Sealing Grease on the sealing surface that contacts the air box. Do not use sealing grease on clamp-on type filters. If a filter is especially difficult to install, it will come with an instruction sheet explaining the correct installation procedure. Keep the instruction sheet with the vehicle for reference anytime the filter is removed. It is very important the filter be installed correctly. The filter can be positioned in the base or the lid, whichever is more convenient and makes the installation easier. Do not use excessive force to install a filter.

If you have any questions regarding the fitting of a Bob's Muffler supplied K&N filter, then please ask before continuing.


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